improvements

[vivi365]

• parsing: avoid parsing the same file with same settings across different analysers (fset)
• reflect: make type checking approach more accurate by fixing importing issue of external dependencies. PR reflection: method invocation approach. #5 wip.

[vivi365]

• parser.go: Change single case switches to direct type assertion.

ast.Inspect(node, func(n ast.Node) bool {
switch x := n.(type) {
  case *ast.CallExpr:

// can be something like
  if fn, ok := n.(*ast.CallExpr); ok { ..
  }
}